Phase-contrast enhanced computed tomography

ABSTRACT

A phase-contrast x-ray computed tomography scanner, a monochromatic diffraction computed tomography scanner, a rotatable monochromatic diffraction computed tomography scanner, and a combination phase-contrast and monochromatic computed tomography scanner are provided. In addition, a method of identifying an unknown sample is provided.

This application is a national phase application under 35 U.S.C. § 371of International Application No. PCT/US02/34605 filed Oct. 30, 2002,which claims priority to U.S. application Ser. No. 10/278,055 filed Oct.22, 2002 and U.S. Provisional Application Ser. No. 60/338,942 filed Nov.5, 2001. The above listed applications are incorporated into thisapplication by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the fields of radiography andtomography. More particularly, this disclosure describes how a standardx-ray source may be used to create phase-enhanced computed tomography(CT) images. These phase-enhanced CT images provide sharper images whichmake small edges, including small masses or small spiculations, moreevident. This provides a method for, among other things, the inspectionof organic materials and for use in medical apparatuses.

2. Description of Related Art

In the conventional x-ray transmission imaging system, the contrast ofan obtained image depends upon the degree of absorption of x-rays by anobject. Namely, if there is a region where heavy elements with highx-ray absorptance are dense, that portion exhibits a low transmittanceand can be caught as a shadow in an image. On the other hand, objectsmade of light elements (soft tissues, etc.) are transparent to x-raysand are therefore difficult to obtain an image contrast. For example, inmany clinical situations, such as mammography, there is a need todistinguish between different kinds of soft tissue, between tumors andnormal tissue, for instance. Accordingly, there is employed a method inwhich the contrast is emphasized by injecting heavy elements as acontrast agent in order to observe biological soft tissues (such asinternal organs, tumors, or blood vessels), for example, when an x-raycross section image for medical diagnosis is to be acquired. However,the contrasting technique cannot always be applied to all observationlocations to be investigated. Also, the contrasting process maynegatively impact the body.

The above problem concerning the image contrast exists similarly even inx-ray computerized tomography (CT) which is a three-dimensional,inside-observing technique. A CT scanner x-rays the body from manyangles. The x-ray beams are detected by the CT scanner and analyzed by acomputer. The computer compiles the images into a picture of the bodyarea being scanned. These images can then be viewed on a monitor orreproduced as photographs.

In lieu of x-ray absorption techniques, there is an imaging methodavailable for obtaining a contrast by monitoring x-ray phase shifts. Aphase-contrast x-ray records information from the x-ray beams after theyhave passed through different materials, including biological softtissues. All tissues cause the x-rays to slow down, resulting in what isknown as a phase shift. The size of the shift depends on the type oftissue. Phase-sensitive techniques, which can be understood using waveoptics rather than ray optics, offer ways to augment or complementstandard absorption contrast by incorporating phase information. Also,since phase-contrast relies only on refraction of x-rays, not onabsorption, imaging can be done at higher energies where the absorbedradiation dose can be less, thereby reducing potential damage totissues.

The use of phase-contrast imaging methods enables observation with anexcellent sensitivity which is one-thousand times as high as that in theconventional absorption-contrast method. Thus it may be possible toobserve phase contrast when absorption contrast is undetectable.Furthermore, biological soft tissues can be observed without beingsubjected to a specific contrasting process. Also, even if a contrastagent is used, the choice of a wider variety of contrast agents andcontrasting techniques are possible.

There has been devised a phase-contrast x-ray CT apparatus in whichphase contrast is introduced to the x-ray CT enabling three-dimensionalobservation. U.S. Pat. No. 5,173,928 is specifically incorporated hereinby reference in its entirety. According to the disclosed technique ofthe '928 patent, an x-ray interferometer is used to reconstruct an imagein a virtual-cross section from interference patterns. This disclosedtechnique is limited to observing an object having a diameter of onlyseveral millimeters, and therefore is not practical for medicaldiagnosis. Further problems with the above system using the x-rayinterferometer is that (1) in order to ensure coherency, the energy bandof an x-ray beam must be narrowed to obtain a high monochromaticity andhence a bright light source such as synchrotron radiation must be used;and (2) that a precision optical system is required and it is thereforedifficult to handle the system.

There has also been devised a phase contrast x-ray CT apparatus in whichan x-ray interferometer is not used. U.S. Pat. No. 5,715,291 isspecifically incorporated herein by reference in its entirety. In the'291 patent, the phase distribution is determined from the distributionof refraction angles of x-rays transmitted through an object. However,this disclosure is limited to object rotation to acquire the necessarydata to reconstruct a CT image.

In view of the shortcomings such as those listed above, improvedphase-contrast imaging techniques would be desirable.

SUMMARY OF THE INVENTION

The present invention discloses methods and apparatuses that are capableof obtaining accurate and well-defined x-ray images of samples such assoft tissues in humans. This invention is envisioned for use in medicaldiagnosis purposes but in no way is so-limited. In fact, it may be usedto study any type of sample.

Breast cancer screening is such an example of the applicability ofApplicants invention. Current mammography screening has a very high rateof false positives and false negatives (Fitzgerald, 2001). In apopulation of undiagnosed women advised by their doctors to have regulardiagnostic screening, only five women out of 1000 will actually havebreast cancer (Fitzgerald, 2001). But for that same population, the rateof positive mammograms will be 10% (Fitzgerald, 2001). The ratio offalse positives to true positives is nearly 20:1 and for about 10–20% ofwomen who have palpable abnormalities, the mammograms won't showanything (Fitzgerald, 2001). Mammography screening is such an example ofthe driving need to improve the current phase contrast x-ray CTapparatuses to obtain more accurate and sharper x-ray images of softtissue.

The present invention is applicable but not limited to methods ofcomputed tomography images of sample objects and to medical inspectionapparatuses which employ phase shift technology to obtain computedtomography images.

One embodiment of the present disclosure is to provide an apparatuswhich creates phase-contrasted CT images based on interference effectswhich take advantage of geometry so that both lateral coherence anddemonstration of phase effects result from the manner in which thesource and detector are placed relative to the object. Specifically, theinvention provides for a phase-contrast computed tomography scannerwhich allows the user to obtain phase-contrast, x-ray computedtomography images of a sample object. The samples that can be scanned bythis CT scanner are unlimited. However, in one embodiment, the sampleincludes biological soft tissues. A suitable CT scanner may use apolychromatic x-ray source. There may also be a power supply sourcecoupled to the polychromatic x-ray source to power it, and a firsttranslation stage may be coupled to the power supply source. Arotational stage may be in spaced relation with the translation stageand configured to hold and rotate the sample. The polychromatic x-raysource may be spaced sufficiently far from the rotational stage so thatx-rays reaching the rotational stage are substantially coherent. Thereis a detector in spaced relation with the rotational stage andconfigured to collect phase contrast x-ray data from the sample. Theremay also be second translation stage coupled to the detector and acomputer coupled to the detector and configured to form a computedtomography image of the sample using the phase-contrast x-ray data TheCT scanner may even provide that the computer controls the power supplysource, the first translation stage, the rotational stage, and thesecond translation stage. In another aspect of this embodiment of thepresent disclosure, an existing x-ray source may be interchanged with apolychromatic x-ray source, which would enable the existing x-ray sourceto perform phase-contrast imaging. In yet another aspect of thisembodiment of the present disclosure, a suitable polychromatic x-raysource may include an x-ray tube, a radioactive source and/or asynchrotron radiation source. Finally, the CT scanner may even furtherprovide that the polychromatic x-ray source operates between a 20 and150 kilovoltage potential kVp) and wherein the polychromatic x-raysource is spaced about four meters from the rotational stage.

In another embodiment of this disclosure, there is provided an apparatuswhich creates phase-contrasted CT images based on interference effectsin which both coherence and imaging require the use of perfect crystals.As used herein, a “perfect crystal” is one in which there are nosubstantial point, linear, or planar imperfections. Specifically, thisembodiment of the present invention provides a monochromatic diffractioncomputed tomography scanner which allows the user to obtainphase-contrast, x-ray computed tomography images of a sample object. Thesamples that can be scanned by this CT scanner are unlimited. However,in one embodiment, the sample includes biological soft tissues. This CTscanner may include a polychromatic x-ray source. There is also a powersupply source coupled to the polychromatic x-ray source to power thepolychromatic x-ray source. There is a first translation stage coupledto the power supply source. There is also a pair of rotatable,interchangeable monochromator crystals in spaced relation with thepolychromatic x-ray source. A rotational stage in spaced relation withthe monochromator crystals and configured to hold and rotate the sampleis also included. There is a rotatable, interchangeable analyzer crystalin spaced relation with the rotational stage. There is also a detectorin spaced relation with the analyzer crystal and configured to collectphase contrast x-ray data from the sample. A second translation stagecoupled to the detector and a computer coupled to the detector andconfigured to form a computed tomography image of the sample using thephase-contrast x-ray data also exists. This CT scanner may even providethat the computer controls the power supply source, the pair ofrotatable interchangeable monochromator crystals, the first translationstage, the rotational stage, the rotatable interchangeable analyzercrystal and/or the second translation stage. In another aspect of thisembodiment of this disclosure, the polychromatic x-ray source mayinclude an x-ray tube, a radioactive source and/or a synchrotronradiation source. The CT scanner may even further provide that thepolychromatic x-ray source operates at a range between 20 and 150 kVp.This CT scanner may further provide that the pair of monochromatorcrystals and the analyzer crystal may be selected from a group ofnon-perfect crystals. However, in one embodiment, the pair ofmonochromator crystals and the analyzer crystal may be perfect siliconcrystals. Finally, in yet another aspect of, this present disclosure, anexisting x-ray source can be interchanged with the polychromatic x-raysource which would enable the existing x-ray source to performphase-contrast imaging.

In yet another embodiment of the present invention, a rotatablemonochromatic diffraction computed scanner is disclosed which employsobject rotation, polychromatic x-ray source rotation and detectorrotation to obtain phase contrast images. The samples that can bescanned by this CT scanner are unlimited. However, in one embodiment,the sample may include biological soft tissues. This CT scanner mayinclude a polychromatic x-ray source configured to rotate about thesample. There may also be a power supply source coupled to thepolychromatic x-ray source to power it. There may be a pair ofinterchangeable monochromator crystals that may be in spaced relationwith the polychromatic x-ray source and configured to rotate with thepolychromatic x-ray source about the sample. There may be a fixed stagethat may be in spaced relation with the monochromator crystals andconfigured to hold the sample in a fixed position. There may also be ainterchangeable analyzer crystal that may be in spaced relation with thefixed stage and configured to rotate with the polychromatic x-ray sourceabout the sample. A detector may be in spaced relation with the analyzercrystal and configured to rotate with the polychromatic x-ray sourceabout the sample to collect phase-contrast x-ray data from the sample.There may be a translation stage coupled to the power supply source, thepair of interchangeable monochromator crystals, the interchangeableanalyzer crystal and the detector. There may also be a computer coupledto the detector and configured to form a computed tomography image ofthe sample using the phase-contrast x-ray data. The CT scanner may evenprovide that the computer controls the power supply source and thetranslation stage. In another aspect of this embodiment of the presentdisclosure, the polychromatic x-ray source may include an x-ray tube, aradioactive source and/or a synchrotron radiation source. In yet anotheraspect of this embodiment, the CT scanner may even further provide thatthe polychromatic x-ray source may operate at a range between 20 and 150kVp. Finally, this CT scanner may further provide that the pair ofmonochromator crystals and the analyzer crystal may be selected from agroup of non-perfect crystals. In one embodiment, the pair ofmonochromator crystals and the analyzer crystal may be perfect siliconcrystals.

In still another embodiment of the present disclosure, the relevanttechnology of the phase-contrast computed tomography scanner and themonochromatic diffraction computed tomography scanner are combinedtogether to form a CT scanner which may be used to create phase-contrastCT images. Specifically, the present disclosure provides a combinationphase contrast and monochromatic diffraction computed tomography scannerwhich allows the user to obtain phase-contrast, x-ray computedtomography images of a sample object. The samples that can be scanned bythis CT scanner are unlimited. However, in one embodiment, the samplemay include biological soft tissues. This CT scanner may include apolychromatic x-ray source. There may also be a first translation stagecoupled to the power supply source. There may be a power supply sourcecoupled to the polychromatic x-ray source to power the polychromaticx-ray source. There may also be a pair of rotatable, interchangeablemonochromator crystals in spaced relation with the polychromatic x-raysource and configured to occupy at least two positions, one positionbeing aligned with the polychromatic x-ray source and the other positionbeing out of alignment with the polychromatic x-ray source. A rotationalstage in spaced relation with the monochromator crystals and configuredto hold the sample may also included. There may also be a rotatable,interchangeable analyzer crystal in spaced relation with the rotationalstage and configured to occupy at least two positions, one positionbeing aligned with the sample and the other position being out ofalignment with the sample. There may be a detector in spaced relationwith the rotational stage and configured to collect phase-contrast x-raydata from the sample. There may also be a computer coupled to thedetector and configured to form a computed tomography image of thesample using the phase-contrast x-ray data. This CT scanner may evenfurther provide that the computer controls the power supply source, thepair of rotatable interchangeable monochromator crystals, the firsttranslation stage, the rotational stage, the rotatable interchangeableanalyzer crystal and/or the second translation stage. In another aspectof this embodiment of the present disclosure, the polychromatic x-raysource may include an x-ray tube, a radioactive source and/or asynchrotron radiation source In yet another aspect of this embodiment,the polychromatic x-ray source may operate at a range between 20 and 150kVp. The CT scanner may even further provide that the pair ofmonochromator crystals and the analyzer crystal may be selected from agroup of non-perfect crystals. In one embodiment, the pair ofmonochromator crystals and the analyzer crystal may be perfect siliconcrystals. Finally, in another aspect of this disclosure, an existingx-ray source can be interchanged with the polychromatic x-ray sourcewhich would enable the existing x-ray source to perform phase-contrastimaging.

In yet another embodiment of the present disclosure, there is provided amethod of identifying an unknown sample. This method my includeobtaining a known sample and then obtaining a phase-contrast, x-raycomputed tomography image of the known sample and identify a diffractionpattern for the known sample using the x-ray computed tomography imageof the known sample. Then, associate the diffraction pattern of theknown sample with the known sample in a database. Then, one can obtain aphase-contrast, x-ray computed tomography image of an unknown sample andidentify a diffraction pattern for the unknown sample using the x-raycomputed tomography image of the unknown sample and correlate thediffraction pattern of the unknown sample with the diffraction patternof a known sample using the database to identify the unknown sample. Thesamples that can be scanned by this CT scanner are unlimited. However,in one embodiment, the sample may include biological soft tissues.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings form part of the present specification and areincluded to further demonstrate certain aspects of the presentinvention. The invention may be better understood by reference to one ormore of these drawings in combination with the detailed description ofspecific embodiments presented herein. These drawings illustrate by wayof example and not limitation, and they use like references to indicatesimilar elements. The drawings include:

FIG. 1—is a drawing of a phase-contrast computed tomography scanneraccording to an embodiment of the present disclosure.

FIG. 2—is a drawing of a monochromatic diffraction computed tomographyscanner and a combination phase-contrast and monochromatic diffractioncomputed tomography scanner according to an embodiment of the presentdisclosure.

FIG. 3—is a drawing of a rotatable monochromatic diffraction computedtomography scanner according to an embodiment of the present disclosure.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG. 1 illustrates one possible construction of a phase-contrastcomputed tomography scanner for providing phase-contrast, x-ray computedtomography images of a sample. A polychromatic x-ray source 1 may beconnected to and powered by a power supply source 2. In one embodiment,the polychromatic x-ray source 1 may be selected from a group includingan x-ray tube, a radioactive source and/or a synchrotron radiationsource. The power supply source 2 may operate between a range of 20 and150 kilovoltage potential. The power supply source 2 may be connected toa computer 4. The computer 4 may control the kilovoltage output of thepower supply source 2. In another embodiment, the power supply source 2may be controlled independent of the computer 4. The polychromatic x-raysource 1 may be situated on top of the power supply source 2. The powersupply source 2 may be situated on top of a first translation stage 3.The first translation stage 3 can be maneuvered through an x-axis, ay-axis and/or z-axis by mechanical knobs. However, in one embodiment,the computer 4 may operate and maneuver the first translation stage 3through the x-axis, y-axis and/or z-axis. The polychromatic x-ray source1 may be about 4 meters away from a rotational stage 8 as exemplified byR1 in FIG. 1. The rotational stage 8 may be capable of supporting asample object 9 for the purposes of scanning the sample object 9 withthe polychromatic x-ray source 1. The rotational stage 8 may be situatedon top of a motor 5 in which the motor 5 may be capable of rotating therotational stage 8 360 degrees. The sample object 9 may be placed asuitable distance R2 from the detector 7 to ensure that the detector 7may be able to collect phase-contrast x-ray data from the sample 9.Those of ordinary skill will recognize that R2 may thus vary widely. Thedetector 7 may be capable of detecting x-ray beams after they havepassed through the sample object 9. The detector 7 may be situated ontop of a second translation stage 6. The second translation stage 6 canbe maneuvered through an x-axis, a y-axis and/or z-axis by mechanicalknobs. However, in one embodiment, the computer 4 can operate andmaneuver the second translation stage 6 through the x-axis, y-axisand/or z-axis. The computer 4 may be capable of analyzing the phaseshift of the x-ray beams that have passed through the sample object 9,thus creating a CT image of the sample object 9 on the computer's 4monitor. The computer 4 may also be capable of operating the powersupply source 2, the first translation stage 3, the motor 5 that iscapable of rotating the rotational stage 8 360 degrees, the secondtranslation stage 6, and/or the detector 7.

FIG. 2 illustrates a possible construction of a monochromaticdiffraction computed tomography scanner for providing phase-contrast,x-ray computed tomography images of a sample. A polychromatic x-raysource 1 may be connected to and powered by a power supply source 2. Inone embodiment, the polychromatic x-ray source 1 is selected from agroup including an x-ray tube, a radioactive source and/or a synchrotronradiation source. The power supply source 2 may operate between a 20 and150 kilovoltage potential. The power supply source 2 may be connected toa computer 6. The computer 6 can control the kilovoltage output of thepower supply source 2. In another embodiment, the power supply source 2can be controlled independent of the computer 6. The polychromatic x-raysource 1 may be situated on top of the power supply source 2. The powersupply source 2 may be situated on top of a first translation stage 3.The first translation stage 3 can be maneuvered through an x-axis, ay-axis and/or z-axis by mechanical knobs. However, in one embodiment,the computer 6 can operate and maneuver the first translation stage 3through the x-axis, y-axis and/or z-axis. A pair of interchangeablemonochromator crystals 13 may be affixed to a first rotational motor 12In one embodiment, the pair of interchangeable monochromator crystals 13may be perfect silicon crystals. In another embodiment, the pair ofmonochromator crystals may be selected from a group of non-perfectcrystals. The pair of interchangeable monochromator crystals 13 may beplaced a suitable distance from the polychromatic x-ray source 1 toensure that the x-rays emerging from the monochromator crystals 13 areessentially parallel. Those of ordinary skill will recognize that thisdistance may thus vary widely. A first rotational motor 12 may becapable of rotating the pair of interchangeable monochromator crystals13 360 degrees. The x-ray 1 source may be a suitable distance R1 from asample object 11 to ensure that the x-ray beams traverse the sampleobject 11. Those of ordinary skill will recognize that this distance maythus vary widely. The rotational stage 4 may be capable of supportingthe sample object 11 to be scanned. The rotational stage may be affixedto a motor 5. The motor 5 may be capable of rotating the rotationalstage 4 360 degrees. A rotatable interchangeable analyzer crystal 10 maybe placed in front of the sample object 11 to be scanned. In oneembodiment, the rotatable interchangeable analyzer crystal 10 is aperfect silicon crystal. In another embodiment, the rotatableinterchangeable analyzer crystal 10 may be selected from a group ofnon-perfect crystals. The rotatable interchangeable analyzer crystal 10may be a suitable distance from the sample object 11 to ensure that thex-ray beams emerging from the sample object 11 are directed to theanalyzer crystal 10. Those of ordinary skill will recognize that thisdistance may thus vary widely. The rotatable interchangeable analyzercrystal 10 may be affixed to a second rotational motor 7. The secondrotational motor 7 may be capable of rotating the rotatableinterchangeable analyzer crystal 10 360 degrees. The sample object 11may be placed a suitable distance R2 from the detector 9 to ensure thatthe detector 9 may be able to collect phase-contrast x-ray data from thesample. Those of ordinary skill will recognize that R2 may thus varywidely. The detector 9 may be configured to collect phase-contrast x-raydata from the x-ray beams passing through the sample object 11. Thedetector 9 may be situated on top of a second translation stage 8. Thesecond translation stage 8 can be maneuvered through an x-axis, a y-axisand/or z-axis by mechanical knobs. However, in one embodiment, thecomputer 6 may operate and maneuver the second translation stage 8through the x-axis, y-axis and/or z-axis. The computer 6 may be capableof analyzing the phase shift of the x-ray beams that have passed throughthe sample object 11, thus creating a CT image of the sample object 11on the computer's 6 monitor. The computer 6 may also be capable ofoperating the power supply source 2, the first translation stage 3, thefirst rotational motor 12, the motor 5 that is affixed to the rotationalstage 4, the second rotational motor 7, the second translation stage 8and/or the detector 9. In another embodiment of this invention, anexisting x-ray source may be interchanged with the polychromatic x-raysource 1.

FIG. 2 also illustrates a possible construction of a combinationphase-contrast and monochromatic diffraction computed tomography scannerfor providing phase-contrast, x-ray computed tomography images of asample. A polychromatic x-ray source 1 may be connected to and poweredby a power supply source 2. In one embodiment, the polychromatic x-raysource 1 may be selected from a group including an x-ray tube, aradioactive source and/or a synchrotron radiation source. The powersupply source 2 may operate between a 20 and 150 kilovoltage potential.The power supply source 2 may be connected to a computer 6. The computer6 can control the kilovoltage output of the power supply source 2. Inanother embodiment, the power supply source 2 may be controlledindependent of the computer 6. The polychromatic x-ray source 1 may besituated on top of the power supply source 2. The power supply source 2may be situated on top of a first translation stage 3. The firsttranslation stage 3 may be maneuvered through an x-axis, a y-axis and/orz-axis by mechanical knobs. However, in one embodiment, the computer 6may operate and maneuver the first translation stage 3 through thex-axis, y-axis and/or z-axis. A pair of interchangeable monochromatorcrystals 13 may be affixed to a first rotational motor 12. In oneembodiment, the pair of interchangeable monochromator crystals 13 may beperfect silicon crystals. In another embodiment, the pair ofmonochromator crystals may be selected from a group of non-perfectcrystals. The pair of interchangeable monochromator crystals 13 may beplaced a suitable distance from the polychromatic x-ray source 1 toensure that the x-rays emerging from the monochromator crystals 13 areessentially parallel. Those of ordinary skill will recognize that thisdistance may thus vary widely. The first rotational motor 12 may becapable of rotating the pair of interchangeable monochromator crystals13 360 degrees. In another embodiment of this invention, the firstrotational motor 12 may also be capable of configuring theinterchangeable monochromator crystals 13 into at least two positions,one position being aligned with the polychromatic x-ray source and theother position being out of alignment with the polychromatic x-raysource 1. The x-ray 1 source may be a suitable distance R1 from a sampleobject 11 to ensure that the x-ray beams traverse the sample object 11.Those of ordinary skill will recognize that this distance may thus varywidely. A rotational stage 4 may be capable of supporting the sampleobject 11 to be scanned. The rotational stage may be affixed to a motor5. The motor 5 may be capable of rotating the rotational stage 4 360degrees. A rotatable interchangeable analyzer crystal 10 may be placedin front of the sample object 11 to be scanned. In one embodiment, therotatable interchangeable analyzer crystal 10 may be a perfect siliconcrystal. In another embodiment, the rotatable interchangeable analyzercrystal 10 may be selected: from a group of non-perfect crystals. Therotatable interchangeable analyzer crystal 10 may be a suitable distancefrom the sample object 11 to ensure that the x-ray beams emerging fromthe sample object 11 are directed to the analyzer crystal 10. Those ofordinary skill will recognize that this distance may thus vary widely.The rotatable interchangeable analyzer crystal 10 may be affixed to asecond rotational motor 7. The second rotational motor 7 may be capableof rotating the rotatable interchangeable analyzer crystal 10 360degrees. In another embodiment of this invention, the second rotationalmotor 7 may also be capable of configuring the rotatable interchangeableanalyzer crystal 10 into at least two positions, one position beingaligned with the sample object 11 and the other position being out ofalignment with the sample object 11. The sample object 11 may be placeda suitable distance R2 from the detector 9 to ensure that the detector 9may be able to collect phase-contrast x-ray data from the sample. Thoseof ordinary skill will recognize that R2 may thus vary widely. Thedetector 9 may be configured to collect phase-contrast x-ray data fromthe x-ray beams passing through the sample object 11. The detector 9 maybe situated on top of a second translation stage 8. The secondtranslation stage 8 may be maneuvered through an x-axis, a y-axis and/orz-axis by mechanical knobs. However, in one embodiment, the computer 6may operate and maneuver the second translation stage 8 through thex-axis, y-axis and/or z-axis. The computer 6 may be capable of analyzingthe phase shift of the x-ray beams that have passed through the sampleobject 11, thus creating a CT image of the sample object 11 on thecomputer's 6 monitor. The computer 6 may also be capable of operatingthe power supply source 2, the first translation stage 3, the firstrotational motor 12, the motor 5 that is affixed to the rotational stage4, the second rotational motor 7, the second translation stage 8 and/orthe detector 9. In another embodiment of this disclosure, an existingx-ray source may be interchanged with the polychromatic x-ray source 1.

FIG. 3 illustrates a possible construction of a rotatable monochromaticdiffraction computed tomography scanner for providing phase-contrast,x-ray computed tomography images of a sample. A polychromatic x-raysource 1 may be connected to and powered by a power supply source 2. Inone embodiment, the polychromatic x-ray source 1 may include an x-raytube, a radioactive source and/or a synchrotron radiation source. Thepower supply source 2 may operate between a 20 and 150 kilovoltagepotential. The power supply source 2 may be connected to a computer 5.The computer 5 may control the kilovoltage output of the power supplysource 2. In another embodiment, the power supply source 2 may becontrolled independent of the computer 5. The polychromatic x-ray source1 may be situated on top of the power supply source 2. The power supplysource 2 may be situated on top of a translation stage 3. Thetranslation stage 3 can be rotated 360 degrees and/or may be maneuveredthrough an x-axis, a y-axis and/or z-axis by mechanical knobs. However,in one embodiment, the computer 6 may rotate the translation stage 3 360degrees and/or maneuver the translation stage 3 through the x-axis,y-axis and/or z-axis. A pair of interchangeable monochromator crystals 9may be affixed to the translation stage 3 and may be capable of beingrotated with the polychromatic x-ray source 1 about the sample object 8.In one embodiment, the pair of interchangeable monochromator crystals 9are perfect silicon crystals. In another embodiment, the pair ofmonochromator crystals may be selected from a group of non-perfectcrystals. The pair of interchangeable monochromator crystals 9 may beplaced a suitable distance from the polychromatic x-ray source 1 toensure that the x-rays emerging from the monochromator crystals 9 areessentially parallel. Those of ordinary skill will recognize that thisdistance may thus vary widely. The x-ray 1 source may be a suitabledistance R1 from a sample object 8 to ensure that the x-ray beamstraverse the sample object 8. Those of ordinary skill will recognizethat this distance may thus vary widely. A fixed stage 4 may be capableof supporting the sample object 8 to be scanned. The fixed stage 4 maynot be affixed to the translation stage 3. A interchangeable analyzercrystal 7 can be placed in spaced relation with the sample object 8 tobe scanned. In one embodiment, the interchangeable analyzer crystal 7may be a perfect, silicon crystal. In another embodiment, the rotatableinterchangeable analyzer crystal 7 may be selected from a group ofnon-perfect crystals. The rotatable interchangeable analyzer crystal 7may be a suitable distance from the sample object 8 to ensure that thex-ray beams emerging from the sample object 8 are directed to theanalyzer crystal 7. Those of ordinary skill will recognize that thisdistance may thus vary widely. The interchangeable analyzer crystal 7may be situated on top of the translation stage 3 allowing theinterchangeable analyzer crystal 7, the polychromatic x-ray source 1and/or the pair of interchangeable monochromator crystals 9 to rotateabout the sample object 8. The sample object 8 may be placed a suitabledistance R2 from the detector 6 to ensure that the detector 6 may beable to collect phase-contrast x-ray data from the sample object 8.Those of ordinary skill will recognize that R2 may thus vary widely. Thedetector 6 may be configured to collect phase-contrast x-ray data fromthe x-ray beams passing through the sample object 8. The detector 6 maybe situated on top of the translation stage 3 allowing the detector 6,the polychromatic x-ray source 1, the pair of interchangeablemonochromator crystals 9 and/or the interchangeable analyzer crystal 7to rotate about the sample. The computer S may be capable of analyzingthe phase shift of the x-ray beams that have passed through the sampleobject 8, thus creating a CT image of the sample object 8 on thecomputer's 5 monitor. The computer 5 may also be capable of operatingthe power supply source 2, the translation stage 3 and/or the detector6.

All of the apparatuses and methods disclosed and claimed herein can bemade and executed without undue experimentation in light of the presentdisclosure. While the apparatuses and methods of this invention havebeen described in terms of preferred embodiments, it will be apparent tothose of skill in the art that variations may be applied to theapparatuses and methods and in the steps or in the sequence of steps ofthe methods described herein without departing from the concept, spiritand scope of the invention. All such similar substitutes andmodifications apparent to those skilled in the art are deemed to bewithin the spirit, scope and concept of the invention as defined by theappended claims.

REFERENCES

The following references, to the extent that they provide exemplaryprocedural or other details supplementary to those set forth herein, arespecifically incorporated herein by reference.

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1. A phase-contrast computed tomography scanner for providingphase-contrast, x-ray computed tomography images of a sample,comprising: a polychromatic x-ray source; a power supply source coupledto the polychromatic x-ray source to power the polychromatic x-raysource; a first translation stage coupled to the power supply source; arotational stage in spaced relation with the translation stage andconfigured to hold and rotate the sample; wherein the polychromaticx-ray source is spaced from the rotational stage so that x-rays reachingthe rotational stage are substantially coherent; a detector in spacedrelation with the rotational stage and configured to collectphase-contrast x-ray data from the sample; a second translation stagecoupled to the detector; and a computer coupled to the detector andconfigured to form a computed tomography image of the sample using thephase-contrast x-ray data.
 2. The scanner of claim 1, wherein thecomputer controls the power supply source, the first translation stage,the rotational stage and/or the second translation stage.
 3. The scannerof claim 1, wherein an existing x-ray source is interchanged with thepolychromatic x-ray source which would enable the existing x-ray sourceto perform phase-contrast imaging.
 4. The scanner of claim 1, whereinthe polychromatic x-ray source is selected from the group comprising anx-ray tube, a radioactive source and/or a synchrotron radiation source.5. The scanner of claim 1, wherein the polychromatic x-ray sourceoperates between 20 and 150 kilovoltage potential and wherein thepolychromatic x-ray source is spaced about four meters from therotational stage.
 6. The scanner of claim 1, wherein the polychromaticx-ray source is placed about four meters from the rotational stage.
 7. Amonochromatic diffraction computed tomography scanner for providingphase-contrast, x-ray computed tomography images of a sample,comprising: a polychromatic x-ray source; a power supply source coupledto the polychromatic x-ray source to power the polychromatic x-raysource; a first translation stage coupled to the power supply source; apair of rotatable, interchangeable monochromator crystals in spacedrelation with the polychromatic x-ray source; a rotational stage inspaced relation with the monochromator crystals and configured to holdand rotate the sample; a rotatable, interchangeable analyzer crystal inspaced relation with the rotational stage; a detector in spaced relationwith the analyzer crystal and configured to collect phase-contrast x-raydata from the sample; a second translation stage coupled to thedetector; and a computer coupled to the detector and configured to forma computed tomography image of the sample using the phase-contrast x-raydata.
 8. The scanner of claim 7, wherein the computer controls the powersupply source, the pair of rotatable interchangeable monochromatorcrystals, the first translation stage, the rotational stage, therotatable interchangeable analyzer crystal and/or the second translationstage.
 9. The scanner of claim 7, wherein the polychromatic x-ray sourceis selected from the group comprising an x-ray tube, a radioactivesource and/or a synchrotron radiation source.
 10. The scanner of claim7, wherein the polychromatic x-ray source operates between 20 and 150kilovoltage potential and wherein the polychromatic x-ray source isspaced about four meters from the rotational stage.
 11. The scanner ofclaim 7, wherein the pair of monochromator crystals and wherein theanalyzer crystal are selected from a group of non-perfect crystals. 12.The scanner of claim 11, wherein the pair of monochromator crystals areperfect silicon crystals and wherein the analyzer crystal is a perfectsilicon crystal.
 13. The scanner of claim 7, wherein an existing x-raysource is interchanged with the polychromatic x-ray source which wouldenable the existing x-ray source to perform phase-contrast imaging. 14.A rotatable monochromatic diffraction computed tomography scanner forproviding phase-contrast, x-ray computed tomography images of a sample,comprising: a polychromatic x-ray source configured to rotate about thesample; a power supply source coupled to the polychromatic x-ray sourceto power the polychromatic x-ray source; a pair of interchangeablemonochromator crystals in spaced relation with the polychromatic x-raysource and configured to rotate with the polychromatic x-ray sourceabout the sample; a fixed stage in spaced relation with themonochromator crystals and configured to hold the sample in a fixedposition; a interchangeable analyzer crystal in spaced relation with thefixed stage and configured to rotate with the polychromatic x-ray sourceabout the sample; a detector in spaced relation with the analyzercrystal and configured to rotate with the polychromatic x-ray sourceabout the sample to collect phase-contrast x-ray data from the sample; atranslation stage coupled to the power supply source, the pair ofinterchangeable monochromator crystals, the interchangeable analyzercrystal and the detector; and a computer coupled to the detector andconfigured to form a computed tomography image of the sample using thephase-contrast x-ray data.
 15. The scanner of claim 14, wherein thecomputer controls the power supply source and/or the translation stage.16. The scanner of claim 14, wherein the polychromatic x-ray source isselected from the group comprising an x-ray tube, a radioactive sourceand/or a synchrotron radiation source.
 17. The scanner of claim 14,wherein the polychromatic x-ray source operates between 20 and 150kilovoltage potential and wherein the polychromatic x-ray source isspaced about four meters from the rotational stage.
 18. The scanner ofclaim 14, wherein the pair of monochromator crystals and wherein theanalyzer crystal are selected from a group of non-perfect crystals. 19.The scanner of claim 18, wherein the pair of monochromator crystals areperfect silicon crystals and wherein the analyzer crystal is a perfectsilicon crystal.
 20. A combination phase-contrast and monochromaticdiffraction computed tomography scanner for providing phase-contrast,x-ray computed tomography images of a sample, comprising: apolychromatic x-ray source; a power supply source coupled to thepolychromatic x-ray source to power the polychromatic x-ray source; afirst translation stage coupled to the power supply source; a pair ofrotatable, interchangeable monochromator crystals in spaced relationwith the polychromatic x-ray source and configured to occupy at leasttwo positions, one position being aligned with the polychromatic x-raysource and the other position being out of alignment with thepolychromatic x-ray source; a rotational stage in spaced relation withthe monochromator crystals and configured to hold the sample; arotatable, interchangeable analyzer crystal in spaced relation with therotational stage and configured to occupy at least two positions, oneposition being aligned with the sample and the other position being outof alignment with the sample; a detector in spaced relation with therotational stage and configured to collect phase-contrast x-ray datafrom the sample; and a computer coupled to the detector and configuredto form a computed tomography image of the sample using thephase-contrast x-ray data.
 21. The scanner of claim 20, wherein thecomputer controls the power supply source, the pair of rotatableinterchangeable monochromator crystals, the first translation stage, therotational stage, the rotatable interchangeable analyzer crystal and/orthe second translation stage.
 22. The scanner of claim 20, wherein thepolychromatic x-ray source is selected from the group comprising anx-ray tube, a radioactive source and/or a synchrotron radiation source.23. The scanner of claim 20, wherein the polychromatic x-ray sourceoperates between 20 and 150 kilovoltage potential and wherein thepolychromatic x-ray source is spaced about four meters from therotational stage.
 24. The scanner of claim 20, wherein the pair ofmonochromator crystals and wherein the analyzer crystal are selectedfrom the group of non-perfect crystals.
 25. The scanner of claim 20,wherein the pair of monochromator crystals are perfect silicon crystalsand wherein the analyzer crystal is a perfect silicon crystal.
 26. Thescanner of claim 20, wherein an existing x-ray source is interchangedwith the polychromatic x-ray source which would enable the existingx-ray source to perform phase-contrast imaging.
 27. A method ofidentifying an unknown sample, comprising: obtaining a known sample;forming a phase-contrast, x-ray computed tomography image of the knownsample; identifying a diffraction pattern for the known sample using thex-ray computed tomography image of the known sample; associating thediffraction pattern of the known sample with the known sample in adatabase; forming a phase-contrast, x-ray computed tomography image ofan unknown sample; identifying a diffraction pattern for the unknownsample using the x-ray computed tomography image of the unknown sample;and correlating the diffraction pattern of the unknown sample with thediffraction pattern of a known sample using the database; therebyidentifying the unknown sample.
 28. The method of claim 27, wherein theknown and unknown samples are soft tissue samples.
 29. The method ofclaim 28, wherein the known and unknown samples are biological softtissue samples.